Sidelobes are encountered in antenna engineering where one or more portions of a radiation pattern do not form a main lobe (e.g., acting in a preferred direction), but rather are formed at various undesired angles and/or directions relative to the main lobe. FIG. 17 provides a representation of a main lobe in conjunction with a plurality of sidelobes. As illustrated in FIG. 17, a main lobe 1710 is engendered in a desired direction (i.e., the main lobe axis). However, rather than all of the radiation pattern forming the main lobe, as illustrated, sidelobes 1720 and a backlobe 1730 can also be formed. Hereinafter the sidelobes 1720 and backlobe 1730 are referred to in combination as sidelobes 1720. In transmitting antennas, excessive sidelobe radiation can waste energy and may cause interference to other equipment operating in conjunction with an antenna array. In receiving antennas, sidelobes may cause interfering signals to be detected, and further increase the noise level in the receiver leading to degradation in signal quality.
An approach to overcome such potentially deleterious effects is to utilize one or more attenuators to facilitate a reduction in the magnitude of the sidelobes 1720. However, antenna systems may be utilized in a lower power system, such as an unmanned aerial vehicle (UAV) which has limited onboard power, and hence, energy consumption of an antenna system is to be minimized as a function of increasing the operational capability (e.g., range, flight time) of the UAV.
In another approach, an array of sub-antennas can be employed to reduce magnitude of sidelobes, where sub-antennas in the array are designed to operate in a specific manner to minimize the occurrence of the sidelobes 1720. Such an array, however, may require a plurality of different sub-antenna configurations to achieve the required operational differences between a first sub-antenna (or first radiator) and a second sub-antenna (or second radiator). For example, in a system where the sub-antennas are formed on a supporting substrate, one or more vias may be required to electrically couple one layer (e.g., a ground layer) with a second layer (e.g., a transmission/receive (T/R) stripline), whereby to achieve a desired effect, placement of respective vias may differ between the first sub-antenna and the second sub-antenna. Furthermore, even though a via connects one electrical path with another electrical path, a single via may not be sufficient to direct a desired volume of electrical energy from the first layer to the second layer, and hence a plurality of vias (e.g., a via field) may be necessary to facilitate the desired transfer of electrical energy across the various sub-antenna layers. Vias can also fail (e.g., owing to thermal cycling during operation of an antenna array) which can negatively affect the reliability of an antenna array.
Thus, while an antenna array, either comprising a single radiator element or a plurality of radiator elements, provides the ‘eye to the world’ for a system (e.g., a UAV), numerous considerations affect applicability and operation of the antenna array. For example, numerous phase array antennas are in operation but are narrow band, e.g., approx. 5% fractional bandwidth, operating with sidelobe levels (SLLs) of approximately 20 dB. Thus, numerous challenges face an antenna designer in achieving increased bandwidth, improved SLLs, reduction in component complexity, while keeping to an absolute minimum power requirements for operation of the antenna.